Patent GB-853042-A (GB)
Title: Improvements in and relating to electrically operated printing devices
Inventor: HAWKES JOHN CECIL
IPC: H04L17/24
Filed: 1958-05-14
Abstract: 853,042. Printing-telegraph receivers. GOVERNMENT COMMUNICATIONS CENTRE, DIRECTOR OF. May 14 1958, No. 15556/58. Class 40(3). A printing telegraph receiver comprises a rotatable type-bearing member, a brush member co-operating with a commutator having a plurality of mutually insulated segments, a rotatably mounted shaft having the type-bearing member and the brush member rotatable therewith, and having an armature constrained to rotate therewith but movable axially of the shaft into frictional engagement either with a member driven by an electric motor or with a rotation-arresting member, means for energizing a selected one of the commutator segments in dependence on an electrical signal and electromagnetic means responsive to the brush engaging the energized segment to displace the armature from engagement with the driven member to engagement with the rotation-arresting member The type-wheel 10 provided with two rows 12, 13 of type is secured to a shaft 11 passing through a magnet 25 and carrying brushes 17, 18 engaging a continuous ring 19 and insulated segments 20 of a commutator 21. A sleeve 27 rotatably mounted on the shaft 11 carries a gear 32 meshing with a gear 33 driven from a shaft 34 and has a flange carrying a ring 28 of friction material engaged by the armature 29 when the magnet 29 is de-energized. The armature is secured by springs 30 to a collar 31, and, in the attracted position, engages a layer 26 of friction material on the face of the magnet. When the brush 18 engages a segment 20 marked by the received signal combination, the magnet 25 is energized, the shaft 11 carrying the typewheel is arrested, and after a very short interval during the rotation of the shaft 34 a pivoted lever 38 is rocked so that a detent roller 37 is moved out of a notch 36 in a collar 35 screwed to the magnet 25 and a detent roller 40 engages between the teeth of a correcting wheel 41 to adjust the position of the type-wheel 10. Subsequently a further cam on the shaft 34 raises the paper and inking ribbon against the selected type member of the rows 12 or 13. After the printing operation the lever 38 is rocked to the position shown, and the electromagnet 25 being de-energized, the shaft 11 is driven until the shaft 34 is arrested at the end of a revolution. The case-shift signals control a magnet 14 to operate a lever 15 to bring the appropriate row 12 or 13 opposite the printing position. Character-selection circuit, Fig. 4. The elements of a 5-unit code are applied at terminals 1-5 to five transistor pairs TA, TB providing negative at 1A, 2A- and ground at 1B, 2B- for marks and negative at 1B, 2B- for spaces, with ground at 1A, 2A-. Each segment 20, such as 20Y, 20T is connected to a gate, such as YD, TD connected to respective outputs A, B of the five transistor pairs TA, TB so that for the corresponding code combination all the inputs to the gate are negative and a negative potential is is applied over the brush 17 and continuous ring 19 to an output effecting the energization of the magnet 25. For example, the input to the gate YD for the segment 20 corresponding to the letter Y having the code combination MSMSM is derived from terminals 1A, 2B, 3A, 4B and 5A, all at negative potential to allow a negative pulse to pass over ring 19 to the electromagnet 25. A circuit, Fig. 3, is utilized to apply a pulse of constant length to the brake electromagnet 25 and to allow for the time taken to bring the drum to rest. A pulse 47 from a marked segment 20 passes through a normally open gate 48 and, after differentiation at 49 to the form P<SP>1</SP>Q<SP>1</SP>, the pulse P<SP>1</SP> fires a one-shot multivibrator 50 producing a pulse having a duration slightly greater than the interval PQ and opening gate 51 so that the whole wave form P<SP>1</SP>Q<SP>1</SP> will pass, and the positive portion Q<SP>1</SP> fires a one shot multivibrator 52 which passes a pulse of constant amplitude and duration to the magnet 25 and also to the brake-hold relay 53 which maintains a current in the electromagnet until a cam 54 on the shaft 34 closes a switch 55 to energize a release winding of the relay, and subsequently disengagement of the clutch 45 takes place before the switch 55 is opened. Soon after clutch 45 is re-engaged, contacts of switch 55 open, and deenergization of the release winding of the relay 53 fires a one shot multivibrator 57 which operates to close the gate 48 for a predetermined period after the re-engagement of the clutch 45 to allow the drum sufficient time to reach its appropriate speed.